Cause:
Wrong port is in being configured or port is blocked
In the example above port 9443 was entered. Port 9443 is the port used by vSphere web client but is not the port used by PowerChute client.

Solution:
PowerChute Network Shutdown by default utilizes ports 443 or 80 to establish communication between the PowerChute client and vCenter Server. Unless you have changed the default port assigned in vCenter Server port 443 or 80 should be selected for communications.